Something black and brown -- that's checked (6)
I believe the answer is:
tartan
'checked' is the definition.
(I've seen this before)
'something black and brown' is the wordplay.
'something black' becomes 'tar' (tar is a black substance).
'and' means one lot of letters go next to another.
'brown' becomes 'tan' (tan is a kind of brown).
'tar'+'tan'='TARTAN'
'that's' is the link.
(Other definitions for tartan that I've seen before include "Cloth with a plaid design" , "Woollen checked material" , "Ship in Mediterranean" , "Scots material" , "Pattern of the Scottish clans" .)